The present invention relates to subterranean treatments and, more particularly, in one or more embodiments, to introducing a relative-permeability modifier into a subterranean interval ahead of, or in conjunction with, a sealant.
In subterranean treatments, it is often desired to treat an interval of a subterranean formation having sections of varying permeability. Consequently, it may be difficult to obtain a uniform distribution of the treatment fluid throughout the entire interval. For instance, the treatment fluid may preferentially enter portions of the interval with high permeability at the expense of portions of the interval with lesser permeability. In some instances, these intervals with variable permeability may be water-producing intervals. In other instance, the portion of an interval with high permeability may be an elbow or turn in a well bore, into which the treatment fluid may preferentially enter. In yet another embodiment, the portion of an interval with high permeability may be a junction of a multi-lateral well, into which the treatment fluid may preferentially enter.
In an attempt to facilitate the uniform distribution of sealants throughout an entire interval, a variety of techniques have been used to divert the sealant to less permeable portions of the interval. For example, when the goal is to seal inflow from a long interval with multiple sections of varying permeability, sealants may be placed using packers or other such devices to focus the sealant into target intervals to help insure that the sealant does not travel into only the sections with relatively high permeability. Other such techniques may have involved, among other things, the injection of particulates, foams, or blocking polymers (e.g., crosslinked aqueous gels) into the interval so as to plug off the high-permeability portions of the subterranean formation, thereby diverting subsequently injected fluids to less permeable portions of the subterranean formation. While each of these diversion techniques has been used successfully, there may be disadvantages. Plugging off the high-permeability sections may not be suitable for a producing interval, for example, because the injected solution (or material) may reduce or stop the flow of hydrocarbons in addition to the achieving a desired diversion of the treatment fluid. Therefore, to return the interval to production, expensive and/or time-consuming remedial treatments may be required to remove the injected solutions (or materials). Furthermore, techniques geared toward injecting solutions (or materials) designed to plug off high-permeability intervals of the formation may require expensive zonal isolation, which may be inaccurate, leading to inadvertent plugging of and/or damage to the hydrocarbon-bearing sections.